McGregor (19-2) wanted Diaz. So did the UFC. It took more than 24 hours of negotiations, mostly on the topics of money and weight, to make it happen, but Diaz eventually agreed to fill in. He will meet McGregor in a 170-pound contest, on 11 days' notice, at UFC 196 in Las Vegas.
But during a Wednesday news conference held at the UFC Gym here, 15 miles south of Los Angeles, McGregor made one thing clear: Diaz is a very nice extra on the set, but the spotlight is still on one man.
"Conor McGregor is fighting, and that's it," McGregor told ESPN.com. "That's all you need to know. That's all I need to know, that's all the fans need to know, and it's all UFC execs need to know. That's why they high-five each other every time, as long as the real draw is on the card."
As he has done so many times before, McGregor berated Diaz (18-10) during Wednesday's news conference, much to the delight of hundreds in attendance. Diaz, from Stockton, California, received some support, but the majority of the crowd was firmly in McGregor's corner.
McGregor knew it, too. He hurled one insult after another, referring to Nate as the "younger brother" of UFC welterweight Nick Diaz. He said he respected Nate Diaz as an opponent but dismissed him in the same breath as someone who "teaches children's jiu-jitsu classes and takes bike rides with the elderly."
McGregor casually predicted a first-round knockout.
"I just think he's too predictable in everything he does," said McGregor, who will be moving up two weight classes after winning the featherweight title in December. "He neglects other disciplines. That's hampered the Diaz brothers' progression as martial artists. I feel his body will be ripped to shreds. It's a soft frame. The left uppercut will be a nice one. [His] long range is an illusion. The left uppercut will ping him clean."
Diaz, who has fought 21 times in the UFC, struggled to keep up with McGregor at times during the news conference. He landed a few verbal blows, including a suggestion he'd been fighting "grown-ups" while McGregor picked on undersized opponents at 145 pounds.
But he also missed a lot, most notably when he lobbed unconvincing steroid accusations at McGregor, who later referred to them as ridiculous.
Circumstances didn't help Diaz out, either. His microphone cut out several times. At one point, he even felt it necessary to remind the crowd it was a two-man event.
"I bring this show, too," Diaz said. "It's the Diaz show, too. So don't forget about that."
Speaking to ESPN.com, Diaz did go more into detail on how the 170-pound fight was made. He said he was originally willing to drop to 155 pounds, but prolonged negotiations and other circumstances eventually had him standing firm at 165. McGregor ultimately suggested the bout simply be fought at 170.
"The first day [UFC] called and said it was going to happen, I was like, 'All right, I'm going to go work out and try to get this weight down,'" Diaz said. "I agreed to 155. I went through a hard day of training. I stopped eating. I had a mission ahead of me.
"Later that night, several things were going on. UFC said, 'If you don't take the fight under these circumstances, we're not calling back.' I said, 'If you aren't calling me back, I'm going to dinner, and things will be different tomorrow.' They called the next day, and I'm like, 'All right, now I'm only fighting at 165, and that's your fault.'
"I don't have the sparring you need for a fight. Now I'm going to deplete myself, too? I was with it, then they started messing around with the whole situation."
Regardless, the matchup was made, and Diaz says he is "good" with the UFC and has been throughout the past year. According to UFC president Dana White, Diaz signed a two-fight extension in addition to his bout agreement for UFC 196.
So the UFC got its first choice in Diaz and extended his contract in doing so. McGregor got the replacement opponent he wanted, a fight that had been discussed in the past and will now happen sooner than planned. Wednesday's news conference seemed an effective promotion for the event, and that should only heat up next week.
And it will heat up March 5, in the part that really matters.
"There's a respect there between us," McGregor acknowledged Wednesday. "But business is business, and he will be KO'd inside the first round."